Special-purpose vehicles, armored vehicles for example, are employed off-road. Their engine compartments and cooling systems are encapsulated to prevent the vehicles from breaking down due to damage to these components of the vehicle's drive assembly by the penetration of foreign bodies. Both combustion air and engine-cooling air are generally supplied through gratings. The engine compartment generally has two such gratings, one for the incoming and one for the outgoing air. A fan in the vicinity of the incoming-air grating fetches in as much air as is needed, and the used air is allowed to escape on its own through the other grating.
Such gratings are expected to be open enough overall to allow all the requisite air through, whereas their individual interstices must be small enough to keep the foreign bodies out.
The known gratings, the one disclosed in German OS 3 703 716 for example, are composed of parallel lengths of structural steel secured in a frame, their ends welded to the facing areas of its inner surface. The welds are in the way of the incoming air and exposed to the impact of the foreign bodies.
The joints between the section and the frame are affected by the heat of welding and are not as resistant to impact as the original material. Furthermore, it is impossible to weld the section to the frame satisfactorily enough.
The ends of the lengths of structural section in the grating generic to the present invention, disclosed in German 4 028 124 A1, are accordingly designed to fit into matching cutouts in the components of the frame, and can either be removed or not removed from its inner surface. The lengths in one particular embodiment of the generic grating fit into such cutouts, and each is secured against displacement by a frame positioned against the surface of the frame that faces away from the lengths.
There is, however, a drawback to this method of attachment in that even slight deviations in tolerance will allow the lengths to move around in the cutouts.
Lengths of structural grating section like those disclosed in Europe Patent 0 732 234 A2 have recently been developed composed of a combination of materials, a core of metal sheathed in a non-metal, e.g aramide, glass-fiber reinforced plastic, or a similar material.